Prop test results?

[TEX 54]

Ok,I need to see if I'm on the right track with my prop tests. On a 17' alum. cat hull boat rigged with a 90hp.TLDI on a 6" JP. With the 3 blade alum.prop 13.75x15P, JP down,motor tucked, good holeshot, WOT 5200rpms. Prop will blowout during holeshot at any JP position but all the way down and tucked.
With the 4 blade SS 14x16P in addition to alot of clutch dog rattle,ok hole shot ,JP can be 1/2 way up and motor at level trim no blowouts,can only get 4200rpms at WOT. I'm ok with having to tuck the motor in during holeshot but I would like to be able to get up with the JP raised from the down pos.I know I need to get the rpms up. My thoughts (rookie calc's) are that I need to try a 13 1/4 x 13P SS 4 blade. In alum. a 13.75 x 14P. I am probaly way off but I can take it!

 

[Silvertip]

Re: Prop test results?

Dropping pitch by 2-inches will still give you only 4600 RPM (theoretically) unless the engine is currently lugging so hard it can't get into its power curve. It's certainly worth a try though but I wouldn't buy the 13P. Why are you stuck on a 4-blade? The original 3-blade had you in the right RPM range and other than the blow-out issue seemed right. Working with setup and perhaps trying other 3-blade designs might help. You might want to spend some time just looking at the hull to see if there is something that is causing turbulence which causes the prop to ventilate during hole shot. You might try experimenting more with trim and JP settings. Sometimes just a minor change makes a world of difference.